What is an EEG?
An EEG is a test that detects abnormalities in your brain waves, or in the electrical activity of your brain. During the procedure, electrodes consisting of small metal discs with thin wires are pasted onto your scalp. The electrodes detect tiny electrical charges that result from the activity of your brain cells. The charges are amplified and appear as a graph on a computer screen, or as a recording that may be printed out on paper. Your healthcare provider then interprets the reading.
During an EEG, your healthcare provider typically evaluates about 100 pages, or computer screens, of activity. H
What is an EEG?
An EEG is a test that detects abnormalities in your brain waves, or in the electrical activity of your brain. During the procedure, electrodes consisting of small metal discs with thin wires are pasted onto your scalp. The electrodes detect tiny electrical charges that result from the activity of your brain cells. The charges are amplified and appear as a graph on a computer screen, or as a recording that may be printed out on paper. Your healthcare provider then interprets the reading.
During an EEG, your healthcare provider typically evaluates about 100 pages, or computer screens, of activity. He or she pays special attention to the basic waveform, but also examines brief bursts of energy and responses to stimuli, such as flashing lights.
Why might I need an EEG?
The EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG. People with lesions of their brain, which can result from tumors or stroke, may have unusually slow EEG waves, depending on the size and the location of the lesion. The test can also be used to diagnose other disorders that influence brain activity, such as Alzheime's disease, certain psychoses, and a sleep disorder called narcolepsy. The EEG may also be used to determine the overall electrical activity of the brain (for example, to evaluate trauma, drug intoxication, or extent of brain damage in comatose patients). The EEG may also be used to monitor blood flow in the brain during surgical procedures. There may be other reasons for your healthcare provider to recommend an EEG.
What happens during an EEG?
An EEG may be done on an outpatient basis, or as part of your stay in a hospital. Procedures may vary depending on your condition and your healthcare provider's practices. Talk with your healthcare provider about what you will experience during your test. Generally, an EEG procedure follows this process:
- You will be asked to relax in a reclining chair or lie on a bed.
- Between 16 and 25 electrodes will be attached to your scalp with a special paste, or a cap containing the electrodes will be used.
- You will be asked to close your eyes, relax, and be still.
- Once the recording begins, you will need to remain still throughout the test. Your healthcare provider may monitor you through a window in an adjoining room to observe any movements that can cause an inaccurate reading, such as swallowing or blinking. The recording may be stopped periodically to let you rest or reposition yourself.
- After your healthcare provider does the initial recording while you are at rest, he or she may test you with various stimuli to produce brain wave activity that does not show up while you are resting. For example, you may be asked to breathe deeply and rapidly for 3 minutes, or you may be exposed to a bright flashing light.
- This study is generally done by an EEG technician and may take approximately 45 minutes to 2 hours.
- If you are being evaluated for a sleep disorder, the EEG may be done while you are asleep.
- If you need to be monitored for a longer period of time, you may also be admitted to the hospital for prolonged EEG (24-hour EEG) monitoring.
- In cases where prolonged inpatient monitoring is not possible, your doctor may consider doing an ambulatory EEG.
Why might I need an EEG?
The EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG. People with lesions of their brain, which can result from tumors or stroke, may have unusually slow EEG waves, depending on the size and the location of the lesion. The test can also be used to diagnose other disorders that influence brain activity, such as Alzheime's disease, certain psychoses, and a sleep disorder called narcolepsy. The EEG may also be used to determine the overall electrical activity of the brain (for example, to evaluate trauma, drug intoxication, or extent of brain damage in comatose patients). The EEG may also be used to monitor blood flow in the brain during surgical procedures. There may be other reasons for your healthcare provider to recommend an EEG.
What happens during an EEG?
An EEG may be done on an outpatient basis, or as part of your stay in a hospital. Procedures may vary depending on your condition and your healthcare provider's practices. Talk with your healthcare provider about what you will experience during your test. Generally, an EEG procedure follows this process:
- You will be asked to relax in a reclining chair or lie on a bed.
- Between 16 and 25 electrodes will be attached to your scalp with a special paste, or a cap containing the electrodes will be used.
- You will be asked to close your eyes, relax, and be still.
- Once the recording begins, you will need to remain still throughout the test. Your healthcare provider may monitor you through a window in an adjoining room to observe any movements that can cause an inaccurate reading, such as swallowing or blinking. The recording may be stopped periodically to let you rest or reposition yourself.
- After your healthcare provider does the initial recording while you are at rest, he or she may test you with various stimuli to produce brain wave activity that does not show up while you are resting. For example, you may be asked to breathe deeply and rapidly for 3 minutes, or you may be exposed to a bright flashing light.
- This study is generally done by an EEG technician and may take approximately 45 minutes to 2 hours.
- If you are being evaluated for a sleep disorder, the EEG may be done while you are asleep.
- If you need to be monitored for a longer period of time, you may also be admitted to the hospital for prolonged EEG (24-hour EEG) monitoring.
- In cases where prolonged inpatient monitoring is not possible, your doctor may consider doing an ambulatory EEG.